20-sim was the first commercially released software package to
support bond graph modeling. The first version of 20-sim with
a bond graph library was released in 1995. Since then a continuous
effort to improve bond graph modeling has made 20-sim the standard
in bond graph modeling.
Bond graphs are a network-like description of physical systems
in terms of ideal physical processes. With the bond graph method,
the system characteristics are split-up into an (imaginary) set
of separate elements. Each element describes an idealized physical
process. To facilitate drawing of bond graphs, the common elements
are denoted by special symbols.
20-sim has a large library containing all standard bond graph
elements. Next to standard element 20-sim supports custom user
made bond graph models.
From the Library Browser (left) you can drag and drop elements into the Graphical Editor (right).
Ports and Multiports
The foundation of bond graph modeling is the use of ports. 20-sim
allows you to create user defined models with an arbitrary number
of power ports and signals. Ports sizes can be 1 (default) or
larger (multiports). For every port you can specify the causality
as fixed preferred, indifferent or depending on the causality
of other ports.
Causal strokes indicate the direction of the efforts and flows
in a bond graph model. In 20-sim, you only have to enter the equations
in one of the possible causal forms. If causality is changed,
the equations are rewritten automatically. 20-sim shows causal
strokes in black color for preferred causality and in causal strokes
in orange color for non-preferred causality. The Causality of
a complete model is derived automatically but can be changed manually.
20-sim will assign causality automatically to your bond graph model.
Algebraic Loops and Differential Causality
Algebraic loops and differential causalities are traced automatically.
If possible, 20-sim will rewrite the equations symbolically to
remove algebraic loops and differential causalities.
Custom Made Models
In 20-sim you can create your own bond graph models and save
them in your own model library. Models can have and arbitrary
number of ports, input and output signals. A specialized drawing
editor can be used to give the models any kind of representation.
Create custom made bond graph elements.
20-sim has an on-board simulator to perform simulation runs.
A number of toolboxes are available to help you analyze your model.
If desired models can be transformed to state space or exported
to Matlab m-files or S-functions.